Horton

Re: reloption to prevent VACUUM from truncating empty pages at the end of relation

Nathan Bossart <bossartn@amazon.com>

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From: "Bossart, Nathan" <bossartn@amazon.com>
To: Andres Freund <andres@anarazel.de>
Cc: Masahiko Sawada <sawada.mshk@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>, Andrew Dunstan <andrew.dunstan@2ndquadrant.com>, Robert Haas <robertmhaas@gmail.com>, "Tsunakawa, Takayuki" <tsunakawa.takay@jp.fujitsu.com>, Alvaro Herrera <alvherre@2ndquadrant.com>, Michael Paquier <michael@paquier.xyz>, Julien Rouhaud <rjuju123@gmail.com>, Laurenz Albe <laurenz.albe@cybertec.at>, "Jamison, Kirk" <k.jamison@jp.fujitsu.com>, Amit Kapila <amit.kapila16@gmail.com>, "Fujii Masao" <masao.fujii@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2019-03-04T22:20:39Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Add TRUNCATE parameter to VACUUM.

  2. Add vacuum_truncate reloption.

  3. Allow VACUUM to be run with index cleanup disabled.

On 3/4/19, 2:05 PM, "Andres Freund" <andres@anarazel.de> wrote:
> On 2019-03-04 22:00:47 +0000, Bossart, Nathan wrote:
>> On 3/4/19, 1:44 PM, "Andres Freund" <andres@anarazel.de> wrote:
>> > Yea, I do think that's a danger. But we allow disabling autovacuum, so
>> > I'm not sure it matters that much... And for indexes you'd still have
>> > the index page-level vacuum that'd continue to work.
>> 
>> I think the difference here is that there isn't something like
>> autovacuum_freeze_max_age to force index cleanup at some point.
>> Granted, you can set autovacuum_freeze_max_age to 2B if you want, but
>> at least there's a fallback available.
>
> Well, but your cluster doesn't suddenly shut down because of index bloat
> (in contrast to xid wraparound). So I don't quite see an equivalent need
> for an emergency valve.  I think we should just put a warning into the
> reloption's docs, and leave it at that.

That seems reasonable to me.

Nathan